Light emitting modules with LEDs (light-emitting diodes) have been provided as a light source for a luminaire in recent years.
In general, a light emitting module has a tendency to decrease an output of the light emitting module and shorten useful life of the light emitting module as a result of rise in LEDs' temperature. It is therefore important to prevent LEDs' temperature from rising in order to prolong the useful life of the light emitting module in a luminaire with the light emitting module. A luminaire with a light emitting module including LEDs to be driven with high-power requires further preventing LEDs' temperature from rising.
For example, JP Pub. No. 2011-150936 (hereinafter referred to as “Document 1”) discloses an LED lighting device having a cooling means such as a fan, and a lighting device.
The LED lighting device described in Document 1 includes LED series circuits and a cooling means driver. The series circuits are connected between output terminals of a DC power supply. The cooling means driver is connected between both ends of a part of the series circuits, including at least one or more LEDs, and configured to cool heat generated by the LEDs. The LED lighting device can effectively prevent its own LEDs' temperature from rising.
A stable voltage can be secured without specially providing the cooling means driver with a power supply. In a case where a fan is employed as a cooling means, the cooling means driver is to drive a fan motor. In this case, the cooling means driver requires a DC voltage of about 6V as DC power for driving the fan motor, and is accordingly supplied with a sum of forward voltages of two LEDs in the series circuit, namely a stable DC voltage of about 6V.
In the LED lighting device of Document D1, there is however difficulty in further preventing LEDs' temperature from rising because only a DC voltage of about 6V is supplied to the fan motor of the cooling means driver.